Changing Employer before the start date

[samiraz]

Hi,

I have an offer from an employer A and I am going to apply for the visa as I have been assigned a CoS already. My start date is set as 24 Feb 2014. I have another offer from employer B but they are completing the RLMT and have informed me that if a suitable worker applies they will withdraw their offer. The problem is employer B will not be able to get back to me till 2nd week of February and if they withdraw I would end up loosing the offer from employer A.

My Questions are as follows:

- Once I get my visa from employer A CoS and I get a CoS from employer B. Will I be able to switch to Employer B using their CoS or would it create a problem if i haven't started the job with employer A ?

- Would UKBA consider my application invalid if I apply immediately after I get my visa from employer A ?

- What would I need to give normal notice to employer A even if i havent started the Job ?

Thank you .
I am reaaly struggling with the questions